Monster Cart Upsell+Free Gift

First of all, you will deal with a "legendery" friendly team. In addition to this, what a great product, "Mate!", you can combine almost three ways to upsell and it works from day one increasing my average cart size in a snap.
I spent hours looking for something (an upsell app) that fit my store (more than 100 collections and 3k products). Try it, that's all I have to say and see by yourself you won't be disappointed.